Looks like with the latest version of the Opal App, you can replicate this yourself!
A ticket checker told me that the bug is fixed in the portable readers but I’m yet to verify this myself.[gfycat data_id="http://gfycat.com/peskygraciousblueshark"]
Here’s a short clip showing how easy it is to replicate.
First scan shows that I’m not tapped on, I then tap on, then again and the tap point shows “already tapped on”
Then I scan again and sure enough tap on failed!